Diagnostic Systems

Diagnostic Systems


Kraeplin (1856-1926) was the founder of modern psychiatry, and the first to classify types of mental disorders by categories of symptoms.

False Dichotomy vs Spectrum

His system, and current diagnostic symptoms, follow the medicinal case of you either have a disorder OR you do not.
However many psychological disorders could be considered more of a spectrum, in that clinical cases of things like anxiety differ from what is considered normal, by factors other than the quality, e.g. the

  • Duration
  • Severity/Extremeness
  • Impairment to lifestyle

However, we have to draw a line somewhere, hard as that is on a spectrum. E.g.


Diagnostic and Statistical Manual of Mental Disorders

The major system in use currently is the DSM, which defines the line between normal and abnormal by using outlined criteria, based on the categories within it.

The overall assessment is determined based on a multi-axial approach, and aims to provide a complete picture of a person's mental health, psychosocial situation and global functioning.

Multi-axial Approach

  • Axes I and II list presently known mental disorders and consider long-standing problems; these usually have set criteria that must be met.
    • e.g. for Bulemia a criteria is "C. The binge eating and inappropriate compensatory behaviours occur, on average, at least twice a week for 3 months.".
  • Axes III, IV and V consider the wider overall functioning of the person.
  1. Most major disorders
    • E.g. Mood disorders, anxiety disorders, schizophrenia, developmental disorders, etc
  2. Long standing chronic conditions
    • Personality disorders, intellectual disabilities
  3. Relevant Medical Conditions
    • E.g. heart conditions could implicate treatment
    • E.g. brain damage could underlie symptoms
  4. Underlying Psychosocial and Environmental Factors
    • E.g. major stressors, economic problems
  5. Global Assessment of Functioning
    • Score between 1 and 100

Assessment Techniques

To ascertain if an individual meets criteria for a mental disorder we can use the following:

  • Diagnostic interviews
  • Self-report questionnaires
  • Reports by significant others
  • Direct observation of behaviour
  • Neuropsychological assessment
  • Psychophysiological assessment (heart rate, brain structure, etc)

Measuring Reports

We have to measure reliability, validity and standardisation of each technique.

  • Reliability: Is the measurement consistent
  • Validity: Does the test measure what it claims to measure
  • Standardisation: The definition of normal must be considered the same (and we already know this is hard to define).